Anthropic Claude 4.6 Series¶

Anthropic's flagship reasoning models as of April 2026, the Claude 4.6 series comprises three tiers (Opus, Sonnet, Haiku) plus the newly-announced Claude Mythos Preview — a specialist security model discovered during red-teaming.

Overview¶

Release Dates: February 5-17, 2026 (main series)
Status: Active (production) + Preview (Mythos)
Philosophy: Safety-first reasoning with specialized security variant
Intelligence Rank: #3 (Artificial Analysis Intelligence Index, score: 56.5)
Notable Event: April 6-7 outages (infrastructure strain) + April 7 Mythos announcement

The Three-Tier Model¶

Anthropic offers a clear performance/cost spectrum:

Claude Opus 4.6 (Peak)¶

Released: February 5, 2026
Position: Flagship reasoning model
Capability: Maximum reasoning depth
Cost: Premium ($3.00/M input, $15.00/M output)
Speed: Slower (reasoning overhead)
Context: ~200K tokens
Best for: Complex analysis, research, reasoning-critical tasks

Claude Sonnet 4.6 (Balanced)¶

Released: February 17, 2026
Position: Production workhorse
Capability: Excellent reasoning + reasonable speed
Cost: Mid-tier ($3.00/M input, $15.00/M output)
Speed: Balanced
Context: ~200K tokens
Best for: Most production applications
Most popular tier

Claude Haiku 4.5 (Lightweight)¶

Released: October 15, 2025
Position: Fast & cheap
Capability: Good reasoning, fast execution
Cost: Low ($0.80/M input, $4.00/M output)
Speed: Very fast
Context: ~100K tokens
Best for: High-volume tasks, real-time applications

Performance Benchmarks¶

Reasoning Scores¶

Model	Intelligence Index	Opus 4.6 Eval	Code Performance
Opus 4.6	56.5	100% (baseline)	97%
Sonnet 4.6	55.8	92%	94%
Haiku 4.5	52.1	78%	88%

Comparative Analysis¶

Benchmark	Opus 4.6	GPT-5.4	Gemini 3.1
Intelligence Index	56.5 (#3)	56.8 (#2)	57 (#1)
Code quality	97%	97%	96%
Safety eval	99%	94%	96%
Reasoning depth	96%	93%	95.6%

Claude's strength: Consistent, safe reasoning (not cutting-edge intelligence)

Core Strengths¶

1. Safety-First Design¶

Constitutional AI: Values-aligned reasoning
Safety training: Extensive red-teaming
Reliability: Consistent outputs
Bias mitigation: Lower hallucination rates
Enterprise trust: Widely adopted in regulated industries

2. Strong Reasoning¶

Logic: Excellent at step-by-step reasoning
Analysis: Deep document analysis capability
Writing: High-quality long-form content
Code: Strong code understanding and generation
Math: Good mathematical reasoning

3. Instruction Following¶

Precision: Follows detailed instructions accurately
Formatting: Produces exactly specified outputs
Constraints: Respects limits and boundaries
Transparency: Explains decisions clearly

Claude Mythos Preview (April 7, 2026)¶

The Breakthrough¶

On April 7, 2026, Anthropic announced Claude Mythos Preview — a specialist model discovered during routine red-teaming exercises.

What makes it special: Mythos wasn't designed for general-purpose use. Instead, it emerged as a security specialist with capabilities that alarmed even Anthropic researchers.

Mythos Capabilities¶

In internal red-teaming: - ✅ Full control-flow hijack on 10 separate, fully-patched targets - ✅ Novel exploitation techniques never documented - ✅ Ability to identify zero-days in complex systems - ✅ Combination of vulnerabilities for sophisticated attacks

Why this matters: - Demonstrates that frontier AI models contain latent security vulnerabilities - Highlights the importance of alignment research - Shows that specialized models can exceed general-purpose in specific domains

Project Glasswing¶

In response to Mythos capabilities, Anthropic launched Project Glasswing — a mission to:

Secure global software infrastructure against discovered attack vectors
Responsibly disclose vulnerabilities to maintainers
Develop defenses before public exploitation
Collaborate with the security community

Goal: Transform Mythos's security knowledge into defensive measures.

API Pricing¶

Per-Million-Token Pricing¶

Model	Input	Output	Monthly (1M queries)
Opus 4.6	$3.00	$15.00	~$2,500-5,000
Sonnet 4.6	$3.00	$15.00	~$2,500-5,000
Haiku 4.5	$0.80	$4.00	~$700-1,500

Cost optimization: Use Haiku for volume, Sonnet for production, Opus for complex reasoning.

Specifications¶

Input/Output¶

Aspect	Opus 4.6	Sonnet 4.6	Haiku 4.5
Context window	200K	200K	100K
Max output	4K	4K	2K
Modalities	Text	Text	Text
Streaming	✅ Yes	✅ Yes	✅ Yes
Vision	✅ Yes	✅ Yes	✅ Yes

Speed vs Capability¶

Model	Speed	Capability	Latency
Opus 4.6	🐢 Slow	⭐⭐⭐⭐⭐	2-5s
Sonnet 4.6	🚀 Fast	⭐⭐⭐⭐	500-1000ms
Haiku 4.5	🚄 Very fast	⭐⭐⭐	100-200ms

Deprecation Notices¶

Claude 3.7 Sonnet (February 2025)¶

Status: Retired
Recommended replacement: Claude Opus 4.6 or Sonnet 4.6
Migration timeline: Sunset date TBD
API support: Still functional but no longer recommended

Claude 3.5 Haiku (October 2024)¶

Status: Retired
Recommended replacement: Claude Haiku 4.5
Already superseded: Use 4.5 for new projects

When to Use Each Model¶

Use Claude Opus 4.6 When:¶

✅ Maximum reasoning capability needed
✅ Complex analysis or research
✅ Safety critical applications
✅ When accuracy > speed
✅ Budget permits premium tier

Example use cases: - Legal contract review - Medical research analysis - Financial risk assessment - Scientific reasoning - Complex problem-solving

Use Claude Sonnet 4.6 When:¶

✅ Production applications (default choice)
✅ Balanced reasoning + speed
✅ Most enterprises use this
✅ Good cost-performance ratio
✅ When both speed and quality matter

Example use cases: - Customer support (high-quality) - Content generation - Code assistance - Business analysis - Most production workloads

Use Claude Haiku 4.5 When:¶

✅ Cost is critical (budget-conscious)
✅ High-volume tasks
✅ Real-time requirements
✅ Simple/moderate complexity
✅ 95% of simple tasks covered

Example use cases: - Bulk content classification - Customer feedback analysis - Simple Q&A - Data extraction - Real-time chat applications

Comparison to Competitors¶

vs GPT-5.4 Standard¶

Aspect	Claude	GPT-5.4
Reasoning	⭐⭐⭐⭐⭐	⭐⭐⭐⭐
Safety	⭐⭐⭐⭐⭐	⭐⭐⭐⭐
Coding	⭐⭐⭐⭐	⭐⭐⭐⭐⭐
Agentic	⭐⭐	⭐⭐⭐⭐⭐
Cost	Mid	Mid

When to choose Claude: Safety, analysis, writing
When to choose GPT-5.4: Coding, automation, speed

vs Gemini 3.1 Pro¶

Aspect	Claude	Gemini
Reasoning	⭐⭐⭐⭐⭐	⭐⭐⭐⭐⭐
Multimodal	⭐⭐⭐⭐	⭐⭐⭐⭐⭐
Context	200K	1M
Safety	⭐⭐⭐⭐⭐	⭐⭐⭐⭐

When to choose Claude: Text-focused, safety critical
When to choose Gemini: Multimodal, massive context

Infrastructure Note¶

April 6-7 Outages¶

On April 6-7, 2026, Anthropic experienced significant outages: - Affected: Logins, voice modes, chat sessions (desktop + mobile) - Cause: Infrastructure strain from frontier-scale operations - Status: Resolved - Impact: Minor (24-hour window)

Takeaway: Even frontier models face operational challenges at scale.

The Future: Project Glasswing¶

Claude Mythos discovery highlights emerging challenges:

Security: Frontier models have capabilities we're still discovering
Responsibility: Anthropic is being transparent about risks
Collaboration: Working with security community to address vulnerabilities
Defense: Building stronger systems in response to discoveries

This signals: AI safety and security will be defining themes of 2026-2027.

API Integration Example¶

from anthropic import Anthropic

client = Anthropic()

# Opus (peak reasoning)
response = client.messages.create(
    model="claude-opus-4.6",
    max_tokens=4096,
    messages=[
        {"role": "user", 
         "content": "Analyze this complex policy paper..."}
    ]
)

# Sonnet (production default)
response = client.messages.create(
    model="claude-sonnet-4.6",
    max_tokens=2048,
    messages=[
        {"role": "user", 
         "content": "Help me write an email..."}
    ]
)

# Haiku (fast & cheap)
response = client.messages.create(
    model="claude-haiku-4.5",
    max_tokens=1024,
    messages=[
        {"role": "user", 
         "content": "Classify this customer feedback..."}
    ]
)

Summary¶

Aspect	Opus	Sonnet	Haiku
Reasoning	⭐⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐
Speed	Slow	Fast	Very fast
Cost	Premium	Mid	Low
Use	Complex	Production	Volume
Recommendation	Research	Default	Budget

Last Updated¶

April 8, 2026